Fuse lock



May 7, 1929. F. w. vERICKSON FUSELOCK Filed Jan. 5l, 1928 Fatented May 7, i929.

UNITED STATES FREDERIC W. ERICKSON, OF L-ARGHMONT, NEW YORK.

FUSE LOCK.

Application filed January 31, 1928.

rllhis invention relates to means for ensuringn the maintenance of a fuse in an electrical circuit as a protection or safety device in the event that an improper connection has been made to replace an ordinary cutout or fuse plug.

Dangerous conditions exist in many electrical installations when'- the fuse plugs that are'employed for the protection of branch wiring circuits are replaced by persons who are not familiar with the purpose or object of such safety devices. The rules of the lire underwriters limit the size of the fuse plugs in a. branchcircuit usually to 15 amperes capacity. Similar fuses are obtainn able for use on main wires, which fuses are rated at 20, 25 and 30 amperes. Sometimes these larger fuses are improperly inserted to take the places of 15 ampere blown fuses. Furthermore, many electrical lires have occured and investigations as to the causes have shown that copper cents, metal discs, hair pins and the like have been placed in the plug receptacles of the cutouts in order to reestablish the electrical connections for thercircuits, thereby leaving said circuits without any safety fuse protection.

. The object of my invention is to provide means for guarding against the existence of such dangerous conditions as above mentioned, by the introduction of 4a secondary fusible device which is electrically connected to the circuit between the customary accessible fuse and the current-consuming devices.

With the above mentioned object in view, my invention consists in the construction and combination of members substantially as hereinafter described and claimed.

Of the accompanying` drawings Figure 1 is a plan view, partially diagrammatic, illustrating one embodiment of mv invention.

'Figure 2 is -a side elevation, partly in vertical section, of the chief elements shown in Figure 1.

Figure il is view of my improved fuselock or secondary members, on a larger scale than Figures 1 and 2, showing the protecting case or sleeve in section and in the position which it may occupy before being slid to locked position.

Figure l is an end view and Figure 5 an elevation partly in section, of the secondary fuse case.

Figure 6 is a face or end view of two of Serial No. 250,894.

the members which are illustrated at the left. of Figure 3.

. Figure 7 represents an elevation, partly in section, of the members shown in Figure G.

u Figures 8 and 9 are a side elevation and a race view, respectively, of the locking spring shown in Figure 3. i

Figure 10 represents an elevation, partly broken out, of the connecting members shown near the middle of Figure 3.

Similar reference characters designate similar parts or features in all of the views. ln the embodiment chosen for illustration by Figure 1, my improved fusclock is employed in a circuit which includes lamps indicated diagrammatically t 12 and supplied from a source of power not necessary to illustrate through connections including a bus bar 13 and wire 14, and a fusible leg of the v circuit which includes wire 15. the fuse-carrying members presently descri ed, a strip or link 16, and bus bar 17.

My improvement-s include a plurality of, preferably two, fusible elements inseries, one being protected by a locking mechanism. For convenience of description and not for purposes of limitation, one will be referred to as the primary fusible -link or cutout which may be, as illustrated, a well-known appliance, while the other, which is locked in a case as hereinafter described, will be referred to as the secondary fusible member.

The primary device (Figs. 1 and 2) includes a center' or live contact plate 18 suitably connected to the strip 1G and terminating at the base of the insulating socket 19 which contains the usual conducting shell 20, and the plug 21 which contains the fuse link 22, said plug being of the usual structure to effect electrical contact with the shell 2O and the plate 18.

hlounted to electrically connect with the shell 20 is a strip 23 to which the secondary fuse device is connected by a lug 2l: and binding screw 25. Said secondary fuse device will now bc described.

Referring to Figures 3 and 5, the case 2G has end caps 27, 2S, through which extend, respectively, screw studs 29, 30, said studs being at the opposite ends of the fusible wire 31 which, in practice, has a current-carrying capacity sufficiently higher than that of the primary fuse 22 to act as a barrier to protect the circuit from overload if anyone were to make a connection in place of a fused link` 22 that would permit of an overload that would endanger the circuit. To illustrate, the primary fuse 22 may be of 15 amperes, and the secondary fuse/31 of 20 amperes. The reason for this will be explained presently.

Mounted on the screw stud 30, and secured by a. set screw 32, is a multi-'sided nut (Figures 3 and 6), and also mounted on said stud and clz'impedbetween said nut 33 and the cap 28, is a disk 34 having a plurality of arms or lingers 35 (Figs. 3, 8 and 9). Said disk and its fingers are preferably made of spring metal such as phosphor bronze or spring steel. At' the other end ot' the nut 33 from the disk 34 is a disk 36 of insulating material. A short length of wire 37, insulated, extends from thelug 24 (Fig. 2) throi'lgh a central bore in the disk 36 into the central bore of the nut as best illustrated by Figure 7 which is a view looking in a direction' op )losite to that at the left end of Figure 3. 'lhe' connection or mounting of said short length ot' wire 37 is made permanent at bot-h ends inany suitable manner, as by soldering one'end in a' recess of the lug 24 (Fig'. 2) and the other end in the bore of the nut 33 (Fig. 7).

Screwed to the stud 29 (Fig. is a nut 3S (Figs. 3 and 10) having' a` lug 39 to which the insulated circuit wire is connected as by a binding screw 40.

Before the members described are completely connected, there is slipped onto the wire 15 a protecting case or sleeve 41, preferably made of a frangible substance such as porcelain or glass. Said case or sleeve has af head 42 at one end, an external groove 43 near said head, and an internal conical recess 44. The opening 45 in the head end of the ease is of a size to enable the case to be slipped from its relative posit-ion illustrated by Figure 3, in the direction'ot the arrow a, over the fuse case 26, until the said opening 45 first passes'the spring lingers 35 (compressing them) and iin-ally permits said ingers to spring out into the conical recess 44, thus automatically locking the case 41 in position (Figs. `1 and 2) to protect the secondary fuse 31 in the sense that no access -an be had to the ease 26 which contains said secondary fuse, unless the frangible case or sleeve 41 is iirst broken. The groove 43 in the case`41 facilitates such breaking if and when it is necessary to substitute a new secondary fuse for a blown one.

The opening 45 in the head en'd of the case 41 is multi-sided to correspond with and snugly fit the multi-sided nut 33 when said case is slipped over the locking fingers 35. Since the nut is connectedv firmly to the wire`37, and when the parts'are firstassenr bled is held firmly by the set screw 32 on the stud of' the secondary fuse, said nut can not be rotated. Therefore, when the multi- -wire or connection.

sided opening is fitted over the nut as just described, there can be no such relative rotation of the members as to effect disconnection of the circuit until after unlocking eifected; and such unlocking first requires breaking of the rangible case 41 as described. Such breaking is required in order togain access to the case which contains the secondary fuse 31 for the purpose of renewing said fuse.

rl`he bore 46 at the other end of the case 41 from its head 42 is but slightly larger than the outside diameter ot theinsulated wire 15 (Fig. 3), and is elongated sulliciently to prevent access ot' anything to tamper with the live portion of the electric circuit within the sleeve.

The utility of the structure as a. whole is as follows It' the normal, accessible, primary fuse is 15 amperes or less, and the secondary, locked, fuse is rated at 20 amperes, the circuit has an overload protection of 33%0/0 safety factor. It' the normal 15 ampere fuse blows repeatedly, it is an indication that there is danger in some appliance, or a defective If then the rules ar'e disregarded, and some improper fuse or other device is used to replace the blown normal member, the secondary member will blow and open the circuit. Current can be restored to the circuit only by breaking the locked case or sleeve 41, and this is to be done by an electrician who will, at the same time, correct the fault that caused the' fuse or fuses to blow, and supply proper primary and seconda-ry fuses and a new locking case or sleeve. 4

Having now described my invention, I claim 1. As a protection for an electric circuit having primary and secondary fusible links in series in said circuit, the secondary fuse having a casing provided with a` locking member, and a lrangible case slidablev eudwisc over the casing of said secondary fuse, said rangible case having a portion to interengage with the said lockinglnember of the said secondary fuse casing.

2. As a protection for an electric circuit which includes primary and secondary fusibleI links in series, a casing for the secoiulary fuse, said casing having a locking member, and a frangible case fislidable endwise over the secondary l'use casing, said rangible case having a portion to automatically interlock with the locl'ing member`ot' the said secondary fuse casing.

3. Means for protecting an electric circuit which includes primary and secondary fusible links in series, said means comprising a casing for the secondary fuse, and a frangiblecase enclosing said secondary fuse casing, said frangible case having an internal recess and the secondary fuse casing having spring 10 recess and the secondary fuse casing having yieldable means to coact with the internal. recess of the said frangible case in locking the latter in protecting position, the frangible case also having a weakened portion to facilitate breakage When access to the secondary fuse is necessary.

In testimony whereofl I have affixed my signature.

FREDERIC IV. ERICKSON. 

